Chrome: VTChromizer makes it a snap to scan suspicious sites, files, URLs, and more from within Chrome using the powerful VirusTotal web-based virus and malware scanner.

VirusTotal is a web-based virus scanner that pulls from the databases of dozens of other virus scanning engines and compares the results. Earlier this year we reviewed VTzilla, a Firefox extension that brought VirusTotal scanning to Firefox.
Since then someone has ported the design as a Chrome extension for easy VirusTotal integration under Chrome.

Firefox only (Windows/Mac/Linux): The VTzilla Firefox extension adds a Scan with VirusTotal option…
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After installing the extension a small VirusTotal logo appears on your Chrome toolbar, clicking it pulls up the menu seen in the screenshot here. You can scan all the links on the site you're currently looking at, visit the VirusTotal homepage, or search the VirusTotal database using the hash of a file, a suspicious URL, an organizational tag, or the username of a VirusTotal user (to see the reports they have filed).